Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.95	10.462%	$228.6011	$228.60	$228.60	$228.60
Purchase #2	$120.86	3.864%	$125.53	$125.53	$125.55	$125.50
Purchase #3	$186.29	5.474%	$196.4875	$196.49	$196.50	$196.50
Purchase #4	$105.34	11.289%	$117.2318	$117.23	$117.25	$117.20
Purchase #5	$163.99	10.824%	$181.7403	$181.74	$181.75	$181.70
Purchase #6	$35.36	6.575%	$37.6849	$37.68	$37.70	$37.70
Purchase #7	$53.69	3.401%	$55.516	$55.52	$55.50	$55.50
7 purchase totals =	$872.48		$942.7916	$942.79	$942.85	$942.70